And what is a regular expression that partially excludes the matching of folder names? I was looking for information on the internet, but to no avail. Instead of excluding names, they find what I wanted to exclude. So it works contrary to the intended one.

To limit the results to just folders, include the following in your search:
folder:

You can also use ! in Everything as the NOT operator, for example:
folder: !"folder name"
where folder name is your partial search.

If you wish to exclude paths, by just specifying the start of the path, please try searching for:
regex:"^(?!C:\\program files)"
where C:\\program files is the path you wish to exclude, this would exclude C:\program files and C:\Program files (x86)